Method of an apparatus for atomizing liquid droplets in the sprayjet of a spraying device

ABSTRACT

An arrangement for atomizing a liquid spray in a gaseous jet, according to which the liquid spray to be atomized is introduced into a flow of a gaseous jet so as to create a region of mist preparation into which fine droplets collected in the marginal area of the atomized mist are returned from the area of ejection of the atomized mist.

United States Patent 1191 Locher 1 Feb. 13, 1973 [54] METHOD OF AN APPARATUS FOR [56] References Cited ATOMIZING LIQUID DROPLETS IN THE SPRAYJET OF A SPRAYING UNHED, STATES PATENTS DEVICE 2,035,677 3/1936 Steinke ..239/103 2,826,399 3/1958 Eriksson ..239/428.5 X lnvemorl Otto Loch, lsny/Allgau, Germany 3,251,556 5/1966 Bumham ..239/103 x i 3,425,058 1/1969 Babington ..239/l24 [73] Ass'gnee' 5:"? fir r; r jfi 3,533,553 10 1970 Britzman 239 4285 x G ran ter 3 y/ 3,583,634 6/1971 Sheetz ..239/103 ermany 22 Filed; Oct 13 1970 Primary ExaminerM. Henson Wood, Jr.

Assistant Examiner-John J. Love [21] PP N05 80,399 Attorney-Walter Becker 30 Foreign Application Priority Data [57] ABSTRACT Oct 1 4 1969 German P19 51 812 8 An arrangement for atomizing a liquid spray in a gaseous jet, according to which the liquid spray to be atomized is introduced into a flow of a gaseous jet so [:21 (31. as to create a region of mist preparation into which E 5 g i 220 23 8 fine droplets collected in the marginal area of the atomized mist are returned from the area of ejection of the atomized mist.

8 Claims, 1 Drawing Figure METHOD OF AN APPARATUS FOR ATOMIZING LIQUID DROPLETS IN, THE SPRAYJET OF A SPRAYING DEVICE have not yet been atomized. The formation of a spray 1 mist generally takes place in a continuous air flow or in a so-called oscillating firing device (Schwingfeuergerat). For purposes of explaining the method and apparatus according to the present invention, there will first briefly be set forth what occurs during the production of a spray mist by means of such oscillating firing device.

Explosions or detonations of a certain frequency will in a pipe produce gas colum oscillations upon which pressure waves are superimposed the amplitudes of which are determined to a major extent by the geometric configuration of the pipe. In the pipe there are thus created overpressure and underpressure zones which follow each other chronologically. The pressure maxima and pressure minima differ considerably from the atmospheric pressure. At one point of the oscillating pipe, which point due to the influence of the temperature is in most instances located at the exit, liquid is introduced through a bore. The liquid jet is immediately torn up into finest droplets by the oscillating gas column and due to the high temperature is partially evaporated and is together with the waste gases expelled in the form of a mist.

When large quantities are involved, the short staying time of the liquid droplets in the oscillating pipe will at a gas velocity of approximately 100 Hertz not be sufficient to produce a uniform fine mist. As a result thereof, in the outer marginal region of the mist jet there will remain relatively large liquid droplets which were not affected by the preceding atomization and have the tendency at the pipe end of the mist generator either to collect at the wall of said mist generator or directly following their exit from the pipe to separate from the mist jet.

These liquid droplets are thus lost for the mist jet. Moreover, when using the mist, for instance, for spraying plants, these droplets are extremely undesirable because they may damage the plants to be treated in view of their too high concentration.

It is, therefore, an object of the present invention to catch those liquid droplets which separate from the mist jet and to subjectsaid droplets to a further mist production in order in this way to avoid damage to the plants to be treated while simultaneously saving spray li uid.

This object and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing which illustrates an embodiment of the invention with those parts which are essential for the invention while representing a section through a diagrammatically shown pipe with a mist adapter according to the present invention.

The method according to the invention for atomizing non-atomized liquid droplets in the marginal regions of a mist jet is characterized primarilyin that the liquid droplets are once more conveyed to the mist forming zone. In this connection it is advantageous when the liquid droplets in the mist forming zone are conveyed to an area which has an underpressure.

The device according to the present invention for carrying out the new method provides that the pipe is equipped with an adapter in the form of a tube of a greater cross-section than the pipe while the outer confining wall of said tubular adapter is in the form of a double wall defining an annular chamber between the two walls. This annular chamber serves for returning the liquid droplets to the mist preparing zone.

In thisconnection it is important that the cross-section of the tubular adapter and its connection with the pipe are precisely adapted to each other so that the liquid droplets which leave the inner portion of the adapter at the marginal zones of the mist jet can again return through the annular chamber. Therefore, it is advantageous when the pipe freely extends into the tubular adapter and, more specifically, in such a way that the adapter coaxially surrounds the pipe.

According to a further feature of the invention, the tubular adapter is fixedly connected to the pipe by a sealing wall or, is desired, is detachably connected thereto. In this connection it is important that this wall forms a proper seal between the tubular adapter and the pipe.

According to a further development of the invention, the annular chamber communicates with the inner space of the adapter through bores. These bores serve to feed the liquid droplets, which return through the annular chamber of the adapter, to the mist preparing zone for a further atomization. It is particularly advantageous to provide these bores at areas which are located in the vicinity of or approximately in the plane passing through that end of the pipe which extends into the adapter.

Referring now to the drawing in detail, the pipe 1 forms the rear portion of the air or gas generating pipe and preferably hasthe same diameter as the remainder of the pipe. If the flow velocity seems to be too slow, pipe 1 may be designed as nozzle without a widening portion. The liquid to be atomized is introduced through bore 2 into pipe 1 while the feeding of the liquid to be introduced may be effectedin a pressureless manner or under an overpressure depending on the operation of the air or gas generator. The spray liquid is torn up into finest droplets by the high flow velocity in pipe 1 when it enters the pipe 1 through bore 2. In view of the high temperature in pipe 1, the droplets are partially evaporated and together with the gas column and the waste gases are ejected through the adapter 3 having a greater diameter than pipe 1.

In view of the greater cross-section of the adapter 3 resulting in a sudden increase in width, a so-called overcxpansion of the gas jet is obtained in or directly behind the plane 4 passing through that end of pipe 1 which extends into the adapter 3. As a result thereof, the static pressure in the gas jet drops considerably below the pressure of the outer atmosphere. This underpressure will in view of an impulse exchange in the dead spaces adjacent plane 4 induce an underpressure the absolute magnitude of which is less than the underpressure in the jet cross-section. The magnitude of the differential pressure is determined by the flow velocity which in its turn depends on the energy inherent to the gas jet while it is immaterial in which form this energy is conveyed to the gas jet.

The dead space in the adapter 3 adjacent plane 4 is through bores 5 in communication with the annular chamber 6. In said annular chamber 6 there will therefore likewise be created an underpressure the magnitude of which will, aside from pressure losses, be affected by the magnitude of the cross-section of the bores 5. Since the annular chamber 6 of tube 3 is tightly sealed by wall 7 with regard to pipe 1, it will be appreciated that in the annular chamber 6 from the free end of the adapter 3 a pressure drop will form which is directed counter to the direction of flow in the interior of the adapter 3.

As a result thereof, the desired outer counter flow effect for carrying out the method according to the invention is realized so that the liquid droplets which float in the marginal zone of the mist jet and together with the latter leave the adapter 3 will, in view of the prevailing pressure drop in the annular chamber 6, be returned to the bores 5 and through said bores will be returned to the main flow in the plane 4 whereby the liquid droplets will pass once more into the mist preparing zone.

The function of the apparatus and method according to the invention is, of course, not limited to the specific embodiment shown in the drawing. Similarly, it is possible to use the pressure drop in the annular chamber 6 for purposes of, for instance, admixing cold air or liquid to a hot gas jet. This may be effected as described above in a counter current flow but may also be effected in the same direction of flow or parallel thereto.

It is, of course, also to be understood that the invention is not limited to the specific showing in the drawing but also comprises any modifications within the scope of the appended claims.

What I claim is:

1. A method of atomizing a liquid spray, which includes the steps of: introducing the liquid spray to be atomized into the flow of a gaseous jet thereby creating a region of mist preparation in which the liquid spray is torn into fine droplets and the majority of said droplets is atomized, ejecting the thus formed mist-gaseous mixture in the form of a jet, and returning non-atomized droplets collected from the outer marginal region of said jet of mist-gaseous mixture directly to only said region of mist preparation itself.

2. A method according to claim 1, which includes the step of creating an under-pressure zone in said region of mist preparation, and returning non-atomized droplets collected from the outer marginal region of said jet of mist-gaseous mixture directly to only said under-pressure zone itself.

3. A method according to claim 1, which includes the steps of collecting excess non-atomized droplets, under-pressurizing a zone in the region of mist preparation, and returning the excess droplets directly to the zone of said under-pressurizing in the mist-gaseous mixture.

4. A method according to claim 3, wherein said introducing the liquid spray into the gaseous jet occurs ahead of the zone of said under-pressurizing.

5. A method according to claim 3 wherein said under-pressurizing occurs by sudden widening of crosssection of the gaseous jet, and supplying of nonatomized droplets occurs specifically from outside the gaseous stream in transition to said widening of crosssection.

6. A method according to claim 3 wherein said returning of excess droplets occurs into peripheral streaming in the region of mist preparation.

7. A method according to claim 3 in which said returning of non-atomized droplets occurs parallel to the gaseous jet.

8. A method according to claim 3 wherein there is maintaining of smaller cross-section of flow of nonatomized droplets than cross-section of the gaseous jet. 

1. A method of atomizing a liquid spray, which includes the steps of: introducing the liquid spray to be atomized into the flow of a gaseous jet thereby creating a region of mist preparation in which the liquid spray is torn into fine droplets and the majority of said droplets is atomized, ejecting the thus formed mist-gaseous mixture in the form of a jet, and returning non-atomized droplets collected from the outer marginal region of said jet of mist-gaseous mixture directly to only said region of mist preparation itself.
 1. A method of atomizing a liquid spray, which includes the steps of: introducing the liquid spray to be atomized into the flow of a gaseous jet thereby creating a region of mist preparation in which the liquid spray is torn into fine droplets and the majority of said droplets is atomized, ejecting the thus formed mist-gaseous mixture in the form of a jet, and returning non-atomized droplets collected from the outer marginal region of said jet of mist-gaseous mixture directly to only said region of mist preparation itself.
 2. A method according to claim 1, which includes the step of creating an under-pressure zone in said region of mist preparation, and returning non-atomized droplets collected from the outer marginal region of said jet of mist-gaseous mixture directly to only said under-pressure zone itself.
 3. A method according to claim 1, which includes the steps of collecting excess non-atomized droplets, under-pressurizing a zone in the region of mist preparation, and returning the excess droplets directly to the zone of said under-pressurizing in the mist-gaseous mixture.
 4. A method according to claim 3 wherein said introducing the liquid spray into the gaseous jet occurs ahead of the zone of said under-pressurizing.
 5. A method according to claim 3 wherein said under-pressurizing occurs by sudden widening of cross-section of the gaseous jet, and supplying of non-atomized droplets occurs specifically from outside the gaseous stream in transition to said widening of cross-section.
 6. A method according to claim 3 wherein said returning of excess droplets occurs into peripheral streaming in the region of mist preparation.
 7. A method according to claim 3 in which said returning of non-atomized droplets occurs parallel to the gaseous jet. 